How to prevent reset of camera after initializing trackedEntity?

CesiumJS
1

First I flyTo a location with particular orientation. When the camera animation completes I start animating a pin on a polyline and set viewer.trackedEntity = mypin so the camera starts tracking that pin but the problem is that it also resets my camera orientation which i specified in flyTo. Its exactly above the pin and too much zoomed in. How should I solve this problem? Here is the code:

var entity = viewer.entities.add({

name: ‘Start’,

position: cartesianArray[0],

billboard: {

image: Cesium.buildModuleUrl(‘Assets/Textures/redpin.png’),

verticalOrigin: Cesium.VerticalOrigin.BOTTOM,

scale: 0.6

}

});
viewer.camera.flyTo({

destination: cartesianArray[0],

orientation:{

pitch : Cesium.Math.toRadians(-40),

},

complete: function(){

viewer.trackedEntity = entity;
startAnimation();// pin animates on polyline

},

});

``

2

Hello,

You can try using the viewFrom property on the entity. This is a Cartesian3 property that specifies the position from which the entity should be viewed http://cesiumjs.org/Cesium/Build/Documentation/Entity.html#viewFrom

This is a bit of a complicated problem, you can see the discussion in this thread: https://groups.google.com/forum/?hl=en#!topic/cesium-dev/a8bwwV3BYuE

We also have this GitHub issue written up to try to find a solution for this: https://github.com/AnalyticalGraphicsInc/cesium/issues/3653

Best,

Hannah

3

Hello Hannah,
I have already tried viewFrom property and it didn’t help. When flyTo completes it snaps back to entity’s position ignoring viewFrom property. But i have found a workaround for this problem while experimenting and I am attaching the code in case anybody else faces the same problem:
var entity = viewer.entities.add({

name: ‘Start’,

// viewFrom: new Cesium.Cartesian3(0,0,10000),

position: cartesianArray[0],

billboard: {

image: Cesium.buildModuleUrl(‘Assets/Textures/ic_current_loc.png’),

verticalOrigin: Cesium.VerticalOrigin.CENTER,

horizontalOrigin: Cesium.HorizontalOrigin.CENTER,

scale: 0.5

}

});

viewer.trackedEntity = entity;

viewer.camera.flyToBoundingSphere(new Cesium.BoundingSphere(cartesianArray[0], 10), {

offset: new Cesium.HeadingPitchRange(0.0, Cesium.Math.toRadians(-25), 1000),

complete: function() {

viewer.clock.onTick.addEventListener(function(clock) {

viewer.camera.lookAtTransform(viewer.camera.transform, new Cesium.HeadingPitchRange(viewer.camera.heading + 0.003, Cesium.Math.toRadians(-25), 1000));

//console.log(viewer.camera.transform);

});

tick();

},

});

``

The tick() is actually the function which animates the position of the entity. This way i can set heading, pitch, and zoom according to my wish.
Note: The onTick event listener is just there to rotate my camera by 0.003, so it keeps rotating. If you don’t want it then you can remove it.

4

I am using this approach
....
// save
savedView.offset = viewer.scene.camera.position.clone();
....
// restore
viewer.trackedEntity._viewFrom._value = savedView.offset;

5

Yura-
Yes, i had that issue and solved it by using the 4/14/2017 "chasecam" function example posted by Matt in this thread:
https://groups.google.com/forum/m/#!topic/cesium-dev/-mDNh2qlTZQ
instead of using trackedEntity. The chasecam aporoach retained the camera heading-pitch-roll that I had set before loading the entity.